A method for authenticating an optical network unit (ONU) and devices for an optical line terminal (OLT) and an optical network unit (ONU) where an ONU is not allowed to be migrated in an authorized manner to an OLT of another vendor for use and binds the ONU and a particular vendor. The method also includes, when an ONU goes online, obtaining, by the OLT, first vendor information of the ONU, where the first vendor information is vendor information of a vendor to which the ONU belongs; comparing, by the OLT, the first vendor information with second vendor information, where the second vendor information is vendor information of a vendor to which the OLT belongs; and if a comparison result indicates that the OLT and the ONU belong to different vendors, determining, by the OLT, that authentication on the ONU fails.
